Large-scale oil tank fire extinguishing

Drawing on domestic and foreign tank fire extinguishing examples and fire research results, combined with personal experience of actual combat, from seven aspects put forward the technical and tactical points of fire extinguishing of large-scale oil storage tanks, be regarded as an introduction, and discuss with your colleagues.

Fire Scouting Highlights

After the fire of the tank is fired and the fire brigade arrives, the fire brigade and the fire fighting vehicle shall gather at the windward or lateral wind direction of the catching tank on the spot if the environmental conditions permit. The fire commander will lead the reconnaissance team to conduct fire reconnaissance. Specifically grasp the following two aspects:

1 , the basic situation of the tank farm

The company’s leaders and security technicians will ask for plans for the tank area, identify the location of the combustion tanks in the tank farm, the total storage capacity of the tank farms, the total number of tanks, and the classification of oil storage tanks.

Clarify the conditions surrounding the fire lanes, water sources and tank farms , fixed and semi-fixed fire-fighting facilities, type and storage capacity of fire extinguishing agents, fire walls ( walls ) and sewers, and local wind direction at that time .

2 , the basic situation of the combustion can

Combustion can casket tolerance, the actual oil reservoir, the height between adjacent cans, pitch construction (structure) of the oil to the tank top (observed color of light oil to the outer wall of the tank with the eye Determined ) How long is the fire time ?

Are heavy oils ( crude oil, residual oil ) , light oil crystals ( gasoline, kerosene, diesel oil ) , or water-soluble organic solvents ( methanol, formaldehyde, ether, acetone, etc. ) stored in the combustion tank ? What is the flame? State of combustion, is the tank top fully open, and is there any residual metal objects after the explosion ?

The combustion tanks are metal oil tanks (1 , vault tanks, 2 , no torque tanks, 3 , special structure tanks, one-finger floating roof tanks, expansion roof tanks, lifting roof tanks and truss top tanks, 4 , horizontal tanks ) , or Non-metallic tanks ( reinforced concrete and brick, stone screed ) ?

Fire command position

When a large-scale tank fire is required to establish a fire command headquarters, it is necessary to take into account the convenience of commanders in front of the fire site and the safety of the commanders in the fire command center. The following factors should be taken into consideration when selecting the location:

● must be in the upwind or sidewind direction beyond 100 meters away from the combustion tank ;

● If there are commanding heights outside the tank area, such as hill slopes, tall devices, buildings, etc., they can be used as appropriate to observe the fire.

● The combustion tanks are located in several oil tanks or in the upwind direction of the tank area. In order to prevent chain explosion combustion caused by heat radiation of other oil tanks, the location of the fire field command must be selected outside the tank area. .

Basic methods of combat

When the fire brigade arrives, the counterfeit vehicles fighting at the front should try their best to park in the upwind or crosswind direction, with the front facing the retractable direction in advance, and keep the fire lanes open so that the fire trucks can quickly transfer positions or withdraw.

1 , cooling cover adjacent cans.

After the fire commander arrives at the scene, he must prioritize and eliminate the tactical principles of first controlling and then destroying. First, deploy the force to spray water on the adjacent cans that have not caught fire, and cover the top of the unburned adjacent cans with wet cotton and other objects. The orifices do not allow the vapors to continue to evaporate, ensuring that adjacent cans do not ignite the fire and fire scene.

The distance between the can and the combustion tank is 1 times the diameter of the small dry combustion tank . Under the effect of heat radiation, it will most likely cause explosion and combustion after a period of time. Therefore, the adjacent tanks with final combustion of less than 1.5 times the diameter of the combustion cans should be sprayed with water and covered with the top of the tank in time; there is a thermal insulation layer outside the wall of the heavy oil tanks. Although the water cooling can not directly affect the dry tank wall, It is still necessary to spray water to the heating surface to protect the outer insulation layer of the heavy oil tank from being burned.

In case of windy weather, the spray cooling of the heated surface of the unburned adjacent cans at the downwind and sidewind direction should be strengthened, and the wind direction should be observed. Once the wind direction changes, the cooling direction must also change.

The curtain of water curtains is laid between the combustion cans and the unburned adjacent cans. The cooling effect of the curtains is more severe.   It not only saves troops but also increases the safety factor. Cooling water cooling the unfired adjacent tank wall has a strength of about 0.7 liters / second·meter. In actual combat, it is only necessary to cool the heating surface of the unfired adjacent tank wall, ie half a tank wall.

2 , cooling protection combustion cans.

When the light oil is burned, the oil's liquid surface temperature is not high, only about 80 . C , and has the characteristic that the temperature of the vertical downwards gradually decreases, the heat wave characteristic is not obvious, the burning time is longer, and the high temperature layer does not appear. However, if the height of the liquid surface of the light oil in the combustion tank is only half or less, the wall of the combustion tank will collapse inwards under the effect of flame and high temperature and may be broken. Therefore, in the entire process of fire extinguishing, the upper part of the wall of the combustion tank should be sprayed with water.

The combatant must shoot the water at the top of the tank or slowly sweep back and forth along the top of the tank to allow the water to flow from the top down to the wall of the tank. This saves water and leaves no cooling blanks.

Cooling water should not be injected into the tank, otherwise a large amount of cooling water enters the bottom of the tank and the oil level will rise. Once the oil level rises to the top of the tank, the effective covering thickness of the foam in the tank during fire extinguishing cannot be guaranteed. Inevitably, the fire extinguishing time is greatly delayed.

Cooling Cooling wood burning tank wall strength of about 0.8 l / sec · m; a diameter of 19 mm gun, enrich the water column of 15 meters, about 10 meters to cool the tank wall perimeter.

3 , ready to fire protection water cooling protection at the same time, the general commander of the fire will be based on the size of the combustion canister and the quality of the internal oil products. When the storage of foam concentrate and water is not sufficient to fire, fire can not rush, otherwise it will receive 400 m² combustion things, the strength of the foam mixture supply 8 liters / minute per square meter; 3 minutes to a fire For the calculation, the foam mixture is required and the foam mixture needs 172,800 L / m2 (173 tons ) in 18 minutes . The mixture ratio of protein foam liquid to water was calculated as 7 %, of which 12096 liters of protein foam liquid (12 tons ) and 160,704 liters of water ( 161 tons).

Note: This calculation method is only for reference when fire commanders organize water supply and foam liquid.

Fire extinguishing technical measures

1. Enable tank fire extinguishing device

When the fixed or semi-fixed fire extinguishing device on the combustion can is not damaged, the fixed or semi-fixed fire extinguishing device on the combustion can should first be used to deliver 8 l / min. square to the tank ; the mixing ratio is 7 %.

2. Use mobile firefighting equipment

When the fixed or semi-fixed fire extinguishing device on the combustion canister has been damaged or not installed at all, the mobile fire-fighting equipment of the fire brigade shall be used - the vehicle - mounted foam gun, mobile foam gun, bubble hose, foam gun and remote control to self-extinguish Cannons, etc., and at the same time, spray foam at fixed points in the tank.

The strength of the mixture of protein foam and synthetic foam is 8 liters / min.m2; the mixing ratio is 7 %.

For all mobile fire-fighting equipment, the proportioning valve of the proportional mixer should be aligned with the corresponding index of the foam injection equipment used; the rated injection pressure of the fire truck ( pump ) should also be adjusted to the corresponding index.

With common foam spray equipment main performance parameters:

PQ4 foam gun, working pressure 0.7 MPa, mixed liquid flow 4 l / s, foam volume 25 l / s.

PQ8 foam gun, working pressure 0.7 MPa, mixture flow 8 l / s, foam volume 50 l / s.

PPY32 mobile foam gun, working pressure 0.8 MPa, mixed liquid flow 32 liters / second, foam volume 200 liters / second.

PP48A car foam gun, working pressure 1.2 MPa, mixed liquid flow 48 l / s, foam volume 300 l / s.

PGl6 foam hose, operating pressure 0.5 MPa, mixture flow 16 l / s, foam volume 100 l / s.

Note: The protein foam liquid cannot be used for fires of polar liquids ( water-soluble organic solvents ) such as Pucciol, Sekin, ether, aldehyde, ketone, and carboxylic acid . For alcoholated gasoline ( alcohol content in gasoline exceeds 10 % ) , it is not appropriate to use protein foam to save.

3 , foam liquid and spray method

The use of foam liquid must be targeted for combatting tank fires. At present, foam liquids that extinguish the effects of oil fires are fluorinated protein foam liquids and synthetic foam liquids ( plant-type flame-retardant fire extinguishing agents ) , also known as "Kehuo l ".

The most effective method is to use a high back pressure foam generator to spray the fluorinated protein foam from under the liquid of the oil tank, and at the same time spray dry powder toward the upper oil surface of the oil tank;

Followed by concentrated use of mobile fire fighting equipment to spray foam at a point in the tank. This can greatly reduce the burning rate of the foam and the oil is contaminated when the foam falls into the oil tank, and the foam fire extinguishing effect is most effectively exerted. Better powder while spraying into the tank, the two-pronged approach to accelerate the speed at which fire nearly doubled, having a multiplier effect.  

4 , under the liquid spray foam technology

The use of submerged injection of fluorinated protein foam has three ways: fixed, semi-fixed and mobile. The use of a mobile device can be used to extinguish a fire with a high back pressure foam generator quick connector on a foam tube 30 metres away from the burner .

The supply intensity of the fluoro-foam foam mixture sprayed under the gasoline tanker is 4-6 liters / min.m2, the fluorocarbon foam liquid mixture ratio is 3% , and the foam is injected into the oil at a rate of 1-3 m / s. .

The supply intensity of the fluorocarbon foam mixture jetted under the reduced crude oil and the diesel tank was 6 liters / min·m 2 , the mixing ratio was 6% , and the rate of foam injection into the oil was 3-6 m / s.

5 , water-soluble organic solvent fire

To fight water-soluble organic solvent fires, antifouling foam liquids or synthetic foam liquids should be used. Other foam fluids have large burning rates and are easily dissolved, resulting in poor fire extinguishing efficiency.

The supply strength of the anti-soluble foam liquid and the synthetic foam liquid varies depending on the type of the anti-soluble foam liquid, the synthetic foam liquid, and the type of the water-soluble organic solvent. When used, the intensity of the supply of the foam liquid to be used must be determined based on the brand's performance parameters.

The mixing ratio of antifoaming foam liquid, synthetic foaming liquid and water is 6-7% , and less than 6% will affect the fire extinguishing performance. When the anti-soluble foam liquid is mixed with water, too much zinc octylate will precipitate and affect the fire-extinguishing effect of the anti-solvent foam, so it is necessary to extinguish the fire within 10 minutes. Considering the possibility of repeated saves, adequate anti-foaming foam stocks should be prepared for 30 minutes.

6 , horizontal tank or small oil pool

For small-scale horizontal tanks or small-scale surface oil tank fires, dry powder fire extinguishing agents may be used, but water spray cooling shall be applied to the metal tank walls first. When the dry powder is sprayed, it must be selected in the upwind direction. The firing position of the dry powder gun ( gun ) should be kept at a corresponding distance from the flame so that the sprayed dry powder is spread out in the flame to achieve the best fire-extinguishing effect.

With dry powder gun, gun main performance parameters:

Dry powder gun, injection pressure 0.8-1.4 MPa, spray distance 10-15 meters .

Dry powder cannon, injection pressure 0.8-1.7 MPa, spray distance of about 40 meters .

When the fire in the horizontal tank is being extinguished, and both the horizontal tank and the ground are burning, the ground fire shall be extinguished first, and then the horizontal tank fire shall be extinguished. That is, the order of low height and high height shall be followed; when the horizontal tank ruptures and the torch shape is burned, several branches may be organized. Direct water guns or spray guns are directed at the root of the fire from different angles, and the flow of water intercepts the flame and the oil surface and implements suffocation.

7 , covering the tank top hole

In order to prevent the adjacent unburned adjacent cans from combusting, the asbestos mat, wet quilts, or wet sacks should be used to cover the breathing valve, manhole, and oil port on the top of the adjacent cans, so that the oil vapor in the cans cannot be obtained. Volatile, does not form a fire explosion spread channels.

8 , tank top hole fire extinguishing method

The top hole of the oil tank caught fire. Although it was a torch-like combustion, the pressure inside the tank was not large. The following methods could be used to save the fire: First, send a combatant to the top of the tank to hold a spray gun to extinguish the fire; second, the combatant put on the insulation clothing . Asbestos mats, wet quilts, or wet sacks cover the openings; third, they are sprayed with a cart type dry powder fire extinguisher.

9. It is not advisable to take pouring measures

In view of the differences in the characteristics of oil products and LPG, it is not advisable to resort to emptying tanks when the tanks are overwhelmed but the roof of the tank has caught fire and the adjacent unburnt tanks are nearby. Instead, the tank should be filled with water or refueled so that the surface of the oil can be pumped to the top of the tank to prevent the air in the tank from falling and then the air will enter into an explosive mixed gas space. The adjacent tank will be detonated due to the cooked radiation of the burning tank after being vented. Or because the flow rate of the pouring tank is too fast, a pressure is formed in the fire tank, and a backfire causes an explosion. The more full the oil in the tank, the less dangerous it is to explode.

10 , unified command focused attacks

To prevent fires in tanks from fighting each other, a unified attack order should be issued on the premise of concentrating on the rape force and preparing enough fire extinguishing agents to strive for success in one stroke:

When the heavy oil tank is burning, due to the coke formation on the surface of the oil, the flame will show up and down. When the flame “volts” is a symbol of small combustion intensity of the heavy oil, it is the best time to extinguish the fire.

If the first attack does not work, the injected fire extinguishing agent will increase the oil level in the combustion can. If the oil level has risen to the tank mouth, the next attack must wait for the flash of oil in the combustion tank to burn to a certain depth or to release a part of the bottom water pad and oil, so that the upper tank volume is vacated to restart the attack: The fire extinguishing time will be greatly delayed.

If water is sprayed and foamed into the heavy oil product storage tank with zero breaking pressure, it will not only help thousands of fire extinguishing, but also lead to the occurrence of boiling over and splashing. The fire commander should pay close attention to the burning of the oil in the storage tank and should promptly order the on-site personnel and vehicles to evacuate quickly when it is found that the oil has boiled and splattered precursors.

Boiling Spill Characteristics

Poisoning and splashing are most likely to occur only in heavy oil tank ( pool ) fires.

Generally , the smaller the volume of the heavy oil tank ( pool ) is, the shallower the heavy oil layer is, and the more moisture content in the oil, the faster the time for boiling overflow and splashing will occur, and vice versa.

Boiling and slopping will repeat several times after a certain period of time. Boiling occurs first. After a certain period of time, splatting will occur and it will happen sooner than once. Boiling over, spilled oil can cause a large area of ​​fire, causing casualties and damage to vehicle equipment.

Boiling spilled precursor

After the heavy oil crystal tank ( pool ) fired for half an hour to one hour, the surface of the heavy oil began to roll out fine oil foams, which was inflated and repeated several times.

The color of the flame is dark red, white and bright, and the flame is greatly increased;

Accompanied by fierce "squeaking" sounds, boiling or splattering will occur soon.

Safety Precautions

l Firefighters on front positions should wear insulating clothes and protective masks. If insulation suits are not enough, wet quilts can be wetted. Water gunners should be organized to cover water gunners under adequate personnel equipment.

2. Fire engines and firefighters should not be deployed in the downwind position of the tank to prevent the flame from suddenly slamming when the tank is high.

3. Determine the retreat route for people in emergency situations, and open up obstacles on the retreat route in advance, such as fences and fences. When receiving an emergency retreat order, firefighters in front should quickly and evacuated. When an explosion occurs, firefighters should lie down on the ground or use objects to hide, and then run to evacuation.

4. To rescue the fire in the horizontal tank, the positions of the water gun ( gun ) shall avoid the ends of the horizontal tank to prevent the heads at both ends from flying out of the tank to cause casualties.

5. The scene of fighting by dry fire is very noisy. The emergency retreat order should be given by the general commander of the fire station with a high-power amplified broadcast to ensure that the on-site personnel can hear it promptly.

6. When the oil or water-soluble solvent overflowing the ground is covered with foam, firefighters cannot step into it. Beware of combustible gas escaping after the bubble is stirred, which will lead to rekindling and unnecessary casualties.